CN-122000982-A - Reactive power control method for multiple converter stations of flexible direct-delivery system based on power operation domain

CN122000982ACN 122000982 ACN122000982 ACN 122000982ACN-122000982-A

Abstract

The invention discloses a reactive power control method for a multi-converter station of a flexible direct-current delivery system based on a power operation domain, and belongs to the technical field of offshore wind power flexible direct-current transmission. The method comprises the steps of firstly calculating reactive power requirements of a receiving end converter station according to grid-connected point voltage, reactive power initial values before reactive power fluctuation of the converter station and the like, then analyzing stable operation constraint conditions of the receiving end converter station, wherein the constraint conditions comprise apparent power constraint of the receiving end converter station, alternating current limit constraint of the converter station and alternating current bus voltage constraint of the converter station, determining a steady-state power operation domain of the receiving end converter station by solving constraint condition boundaries, and finally designing an active fast conversion control method considering reactive power fluctuation based on the reactive power requirements and the steady-state power operation domain to realize power mutual and cooperative control among multiple converter stations. The invention can ensure that the offshore wind power flexible direct-delivery system is always maintained in a steady-state power operation area, and improves the reactive power supporting capability and the operation stability of the system.

Inventors

WU QIAN
ZHENG ZHIYUN
YANG ZHICHAO
GAO BINGTUAN
YUAN WEI
ZHENG YUCHAO
WANG LINYUAN
RUAN MENG
WANG YANG
QI WANCHUN
SUN WENTAO
Wang Chuochuo

Assignees

国网江苏省电力有限公司经济技术研究院
国网江苏省电力有限公司
东南大学

Dates

Publication Date: 20260508
Application Date: 20260210

Claims (4)

1. The reactive power control method for the multi-converter station of the flexible direct-delivery system based on the power operation domain is characterized in that the flexible direct-delivery system comprises an offshore wind farm, a plurality of delivery-end converter stations, a land collection switching station, a direct-current transmission sea cable, a direct-current transmission land cable, a high-voltage direct-current overhead line, a plurality of receiving-end converter stations and a receiving-end power grid, and comprises the following steps: step 1, calculating reactive power requirements of a receiving-end converter station according to reactive power value information before reactive power fluctuation of the grid-connected point voltage and the converter station; analyzing stable operation constraint conditions of the receiving-end converter station, wherein the constraint conditions comprise apparent power constraint of the converter station, alternating current limit constraint of the converter station and alternating current bus voltage constraint of the converter station, and determining a stable power operation domain of the receiving-end converter station by solving constraint condition boundaries; and 3, designing an active rapid conversion control method considering reactive fluctuation based on reactive power requirements and the steady-state power operation domain, and realizing power interaction and cooperative control among multiple converter stations.
2. The reactive power control method for a multiple converter station of a flexible direct current delivery system based on a power operation domain according to claim 1, wherein the reactive power requirement of the receiving end converter station in step 1 is as follows: , Wherein Q C,re is the current required reactive power of the receiving end converter station, Q C0 is the reactive power initial value of the converter station before reactive power fluctuation, deltaQ C is the reactive power fluctuation demand of the converter station, deltaI Cq is the reactive current variation of the converter station, namely the current Q-axis component variation, k r is the reactive current proportionality coefficient, deltaU C is the alternating voltage value variation of the converter station, the value of the variable is equal to the difference between the current alternating voltage value U C and the reactive power initial value U C0 before fluctuation, and I CN is the alternating current rated value of the converter station.
3. The reactive power control method for multiple converter stations of a flexible direct current output system based on a power operation domain according to claim 1, wherein the apparent power constraint expression of the receiving end converter station in step 2 is: , Wherein S C is apparent power output by the receiving end converter station, P C is active power output by the receiving end converter station, Q C is reactive power output by the receiving end converter station, k T is the maximum overload coefficient of the receiving end converter station, and S CN is the apparent power rated value of the receiving end converter station; the ac busbar voltage constraint expression of the receiving end converter station is: , Wherein, US is the effective value of the line voltage of the receiving end power grid, XS is the equivalent impedance of the receiving end power grid, and the small-value line resistance is ignored; The ac current limit constraint expression of the receiving end converter station is: , wherein ICmax is the maximum value of alternating current of the receiving end converter station; Combining all the constraint conditions to obtain a power operation domain of the receiving end converter station, if the power of the ith receiving end converter station is operated at a point (P Ci , Q Ci ), outputting an active power maximum limit value of P Cimax , outputting a reactive power maximum limit value of Q Cimax , and if the power of the ith receiving end converter station is operated at a point (P ' Ci , Q Ci,re ) after the reactive power fluctuates, outputting an active power maximum limit value of P' Cimax and outputting a reactive power maximum limit value of Q 'in the power operation domain' Cimax.
4. The reactive power control method for a multiple converter station of a flexible direct delivery system based on a power operation domain according to claim 1, wherein the step 3 designs an active fast transition control method considering reactive power fluctuation based on reactive power demand and the steady state power operation domain, comprising: The method comprises the steps of providing that I current transformer stations in N current transformer stations at the receiving end have reactive power fluctuation, and J (I+J=N) current transformer stations have no reactive power fluctuation, dividing a reactive power interval required by the current transformer stations at the receiving end into two sections, wherein the two sections comprise a reactive power section I and a reactive power section II, and providing that the total wind power of a wind power plant is unchanged in the reactive power fluctuation process; Q Ci,re ≤ Q' Cimax and P Cimax ≤ P' Cimax , wherein the reactive power required by the receiving-end converter stations is within the maximum limit value of the output reactive power of the power operation domain, and the output active power of the I receiving-end converter stations is unchanged, and is expressed as: , And the reactive power section II is Q Ci,re ≤ Q' Cimax and P Cimax > P' Cimax , and in order to preferentially meet the reactive power requirement of the receiving-end converter stations and ensure that the receiving-end converter stations continuously work in a power operation domain, the output active power of the I receiving-end converter stations must be reduced to the maximum limit value of the active power of the power operation domain, which is expressed as: , the reduced active power of the I receiving converter stations requires the other converter stations to convert and all converter station active power variations are expressed as: , Wherein k j is the active power conversion proportionality coefficient of the jth converter station, the value of the active power conversion proportionality coefficient is given according to the electric distance between the converter station and the I converter stations and the reactive fluctuation degree of the I converter stations, delta P C is the active power variation of the receiving end converter station after reactive fluctuation, and P w represents the output power of a wind power plant; representing the active power after the change of the receiving end converter station.

Description

Reactive power control method for multiple converter stations of flexible direct-delivery system based on power operation domain Technical Field The invention relates to a reactive power control method for a multi-converter station of a flexible direct-current delivery system based on a power operation domain, and belongs to the technical field of offshore wind power flexible direct-current transmission. Background With the large-scale access of the deep sea wind power, the voltage immunity of the land power grid is weakened. And by means of the flexible reactive power supporting capability of the flexible direct-current system, the stability of the power grid can be effectively improved. However, when reactive power fluctuation caused by land ac faults, load changes and the like occurs, if the reactive power control cannot be performed in time by the receiving-end converter station, problems such as ac voltage deviation out of limit, system dc overvoltage and even system shutdown can be caused. If the receiving converter station provides reactive support, the output active power may be reduced due to the constraints of the system. In order to transmit as much active power as possible from the wind farm, improving the operational economy, the reduced active power may be converted using the surplus active output capacity of other converter stations. In view of the demands of reactive support capability and operation economy of the flexible direct-delivery system, a set of active rapid transfer control method which is suitable for the flexible direct-delivery system and takes reactive fluctuation into consideration among multiple converter stations is needed to ensure the stability and economy of the system operation. Disclosure of Invention Aiming at the technical problems, the invention aims to provide a reactive power control method of a flexible direct-current delivery system with multiple converter stations based on a power operation domain, which designs an active rapid conversion control method considering reactive power fluctuation by calculating reactive power requirements of a receiving-end converter station and constructing the power operation domain comprising apparent power constraint of the converter station, alternating current limit constraint of the converter station and alternating current bus voltage constraint of the converter station, so that the converter station can always stably operate and power mutual and cooperative control among the multiple converter stations is realized. In order to achieve the purpose, the technical scheme adopted by the invention is that the reactive power control method of the multi-converter station of the flexible direct-delivery system based on the power operation domain comprises an offshore wind power plant, a plurality of delivery end converter stations, an onshore collection switching station, a direct-current transmission sea cable, a direct-current transmission land cable, a high-voltage direct-current overhead line, a plurality of receiving end converter stations and a receiving end power grid, and the method comprises the following steps: step 1, calculating reactive power requirements of a receiving-end converter station according to information such as reactive power values before reactive power fluctuation of the converter station and the like of grid-connected point voltages; analyzing stable operation constraint conditions of the receiving-end converter station, wherein the constraint conditions comprise apparent power constraint of the converter station, alternating current limit constraint of the converter station and alternating current bus voltage constraint of the converter station, and determining a stable power operation domain of the receiving-end converter station by solving constraint condition boundaries; and 3, designing an active rapid conversion control method considering reactive fluctuation based on reactive power requirements and the steady-state power operation domain, and realizing power interaction and cooperative control among multiple converter stations. As a preferred mode of the present invention, the reactive power requirement of the receiving-end converter station in the step1 is: In the formula, re is the current required reactive power of the receiving end converter station, QC0 is the reactive power initial value of the converter station before reactive power fluctuation, deltaQC is the reactive power fluctuation demand of the converter station, deltaI Cq is the reactive current variable quantity of the converter station, namely the current q-axis component variable quantity, k r is the reactive current proportionality coefficient, deltaU C is the alternating current voltage value variable quantity of the converter station, the value of the variable quantity is equal to the difference between the current alternating current voltage value U C and the reactive power pre-fluctuation alternating current voltage initial